KevinShaughnessy: I think this is only half an answer in this case. I suppose many customers, including fx1333X (and our org as well) mainly use Exchange Online, but in connection with an OnPrem AD, and therefore the synchronization of users and groups via AADC, because as you certainly are aware of, we need an OnPrem Exchange server to manage certain Exchange Online attributes in a supported way. Like certain properties of distribution groups.
I guess we might use synchronized users, but Cloud-only groups, but that does not really make sense.
I don't know how far the product group is in making the OnPrem Exchange server obsolete for managing Exchange Online, but until that is done, I think you cannot just ignore Exchange OnPrem.